Lernmaterialien für Microscopy an der University of Witwatersrand

• stereo binocular 

  • light reflected off of specimen or through

  • used for dissection

  • can show gross morphology of species 

• high power

  • light transmitted through species

  • used to examine tissues and some cellular detail

• electron beam scans surface of specimen 

• allows for detailed examination of surface structures 

• looks 3d

• electron beams transmitted through specimen 

• examination of very small structures eg viruses and organelles

• millimeter- mm 1x10^-3m

• micrometer- μm 1x10^-6m

• nanometer-nm 1x10^-9m

• picometer- pm 1x10^-12m

• intermediate image reversed

• retina image flipped again

• brain flips image when processing

• virtual image is reversed of actual specimen

• numerical aperture of the objective lens 

• wave length of the radiation used to form the image 

0.61λ/N.A.

• aberrations in the lens used 

• specimen thickness

• specimen contrast 

• chromatic

  • rays of different wavelengths from a point in the specimen focus at different distances resulting in an unsharp image 

• spherical

  • rays from different points in the specimen that pass through diff regions of the lens, focus at diff distances resulting in an unsharp image 

• field curvature 

  • a flat specimen is shown as curved so the centre and edges cant be focused simultaneously 

• light rays refracted at upper surface 

• high power objectives designed to correct this refraction

• w/out cover slip, the objective is under corrected -spherical aberration

microscopes are used to render visible objects that are too small to be seen by the naked eye